Nailing your sustainability case interviews is critical if you're targeting sustainability consulting roles. I’m a former Bain Manager and interviewer and this guide covers everything from the types of cases you'll see to the technical knowledge interviewers expect you to know.

 

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What Makes Sustainability Cases Different

 

Sustainability cases follow the same structure as traditional consulting cases. You'll still need to create frameworks, perform calculations, and deliver recommendations.

 

The difference is in the complexity and constraints.

 

Traditional profitability cases might ask "Should this company expand into a new market?" A sustainability case asks "Should this company expand into a new market while cutting emissions 40% and ensuring zero waste to landfill?"

 

You're solving for multiple objectives simultaneously. Financial returns matter, but so do carbon reductions, water usage, social impact, and regulatory compliance.

 

Three things make sustainability cases harder than traditional cases:

 

1. You may need some technical knowledge. You can't fake understanding carbon accounting or renewable energy economics. Interviewers will quickly spot if you don't know the basics.

 

2. Success metrics are multidimensional. Profit isn't the only measure. You might optimize for carbon reduction per dollar spent, or balance job creation against emissions cuts.

 

3. Stakeholders are more complex. You'll deal with regulators, NGOs, local communities, and investors who all define success differently.

 

Common Types of Sustainability Cases

 

Most sustainability cases fall into six categories. Here's what to expect in each.

 

1. Carbon Reduction Strategy Cases

 

These cases ask how a company should reduce its greenhouse gas emissions.

 

Key things to consider:

 

• Current emissions baseline across all scopes

 

• Cost per ton of CO2 reduced for different interventions

 

• Timeline and capital requirements

 

• Regulatory drivers and potential carbon pricing

 

• Technology readiness and scalability

 

The math usually involves calculating emissions reductions and cost per ton abated. You'll compare options like switching to renewable energy, improving efficiency, changing processes, or purchasing offsets.

 

2. Renewable Energy Investment Cases

 

Should a company invest in solar, wind, or other renewable energy? These cases combine traditional investment analysis with energy sector knowledge.

 

You'll evaluate factors like:

 

• Upfront capital costs vs. ongoing savings

 

• Energy generation capacity and utilization rates

 

• Power purchase agreement structures

 

• Grid connection and transmission costs

 

• Government incentives and subsidies

 

• Technology risk and maintenance costs

 

The math centers on calculating payback periods, and net present value of different options.

 

3. Circular Economy Cases

 

These cases focus on eliminating waste and keeping materials in use.

 

Examples include designing take-back programs for electronics, creating packaging made from recycled materials, or implementing industrial symbiosis where one company's waste becomes another's input.

 

Key considerations:

 

• Material flows and waste streams

 

• Economics of collection, sorting, and reprocessing

 

• Product design changes needed

 

• Market for recycled materials

 

• Infrastructure requirements

 

• Customer willingness to participate

 

4. Sustainable Supply Chain Cases

 

These cases involve helping a company make its supply chain more sustainable. You might reduce emissions from logistics, ensure ethical sourcing, eliminate deforestation, or improve labor conditions.

 

Important factors:

 

• Mapping the supply chain and identifying hotspots

 

• Supplier engagement and capacity building

 

• Traceability and certification systems

 

• Cost implications and cost sharing

 

• Risk of supply disruption

 

• Industry standards and collaboration

 

5. Climate Risk Assessment Cases

 

These cases evaluate how climate change threatens a company's operations or investments.

You might assess physical risks like flooding or drought, transition risks from policy changes, or opportunities from changing markets.

 

Key elements:

 

• Time horizons and climate scenarios

 

• Asset exposure and vulnerability

 

• Financial impact modeling

 

• Adaptation options and costs

 

• Disclosure requirements

 

• Insurance and risk transfer

 

6. ESG Strategy Cases

 

Environmental, Social, and Governance cases are broader than pure environmental issues.

You might develop a comprehensive ESG strategy, improve ESG ratings, or respond to investor pressure.

 

You may need to consider:

 

• Material ESG issues for the industry

 

• Current performance vs. peers

 

• Investor and stakeholder expectations

 

• Data collection and reporting systems

 

• Governance structures

 

• Quick wins vs. long-term transformation

 

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Essential Sustainability Technical Knowledge

 

You don't need to be a sustainability expert, but you do need solid fundamentals. Here's what interviewers expect you to know.

 

Carbon Accounting Basics

 

Understand the three scopes of emissions:

 

• Scope 1: Direct emissions from company-owned sources. Think combustion in boilers, company vehicles, or industrial processes

 

• Scope 2: Indirect emissions from purchased electricity, steam, heating, or cooling

 

• Scope 3: All other indirect emissions in the value chain. This includes purchased goods, business travel, employee commuting, product use, and end-of-life treatment

 

Know that Scope 3 is usually 70-90% of a company's total footprint but also the hardest to measure and control.

 

Common Sustainability Metrics and Units

 

You'll work with these units regularly:

 

• Tons of CO2 equivalent (tCO2e): Standard measure that converts all greenhouse gases to CO2 equivalents

 

• Carbon intensity: Emissions per unit of output (like tCO2e per ton of product)

 

• Energy intensity: Energy use per unit of output

 

• Water intensity: Water consumption per unit of output

 

Renewable Energy Economics

 

Understand the basics of how different technologies compare:

 

• Solar and wind are now the cheapest electricity sources in most markets

 

• Levelized Cost of Energy (LCOE) measures total lifetime cost per unit of energy produced

 

• Capacity factor matters - solar and wind don't produce 24/7

 

• Battery storage is becoming economical for 4-8 hour storage

 

• Green hydrogen shows promise but is still expensive

 

Circular Economy Concepts

 

Know these key principles:

 

• Design out waste from the start

 

• Keep products and materials in use

 

• Regenerate natural systems

 

You should understand the difference between recycling (breaking materials down) and reuse or remanufacturing (keeping products intact).

 

Sustainability Case Interview Frameworks

 

Creating frameworks for sustainability cases follows the same process as traditional cases. Here are some common buckets you may need to include in your sustainability case interview framework.

 

Environmental Impact

 

• Carbon emissions across all scopes

 

• Energy and water use

 

• Waste generation and circularity

 

• Biodiversity and land use

 

• Air and water pollution

 

Financial Analysis

 

• Upfront capital costs

 

• Operating cost changes

 

• Revenue impacts

 

• Payback period and NPV

 

• Cost of carbon

 

Technical Feasibility

 

• Technology maturity and availability

 

• Infrastructure requirements

 

• Scalability

 

• Timeline and phasing

 

• Technical risks

 

Stakeholder Considerations

 

• Regulatory requirements and compliance

 

• Investor and lender expectations

 

• Customer preferences and willingness to pay

 

• Employee engagement

 

• Community impact

 

• NGO and activist concerns

 

Strategic Fit

 

How does this align with the broader business?

 

• Consistency with corporate strategy

 

• Brand and reputation effects

 

• Competitive positioning

 

• Risk mitigation

 

• Future-proofing against regulation

 

Here's an example framework for a carbon reduction case:

 

Objective: Reduce emissions 40% by 2030 while maintaining profitability

 

1. Current State

 

• Emissions baseline by scope

 

• Current initiatives and trajectory

 

• Cost structure

 

2. Reduction Options

 

• Energy efficiency improvements

 

• Renewable energy procurement

 

• Process changes

 

• Supply chain interventions

 

• Offsets or removals

 

3. Evaluation Criteria

 

• Cost per ton CO2 reduced

 

• Capital requirements

 

• Implementation timeline

 

• Technical risk

 

• Co-benefits

 

4. Implementation

 

• Sequencing and priorities

 

• Organizational changes needed

 

• Measurement and tracking

 

Solving Quantitative Problems in Your Sustainability Case Interview

 

Sustainability cases involve specific types of math. Here are the most common calculations you'll do.

 

1. Carbon Reduction Calculations

 

You'll often compare different reduction options by calculating tons of CO2 saved and cost per ton.

 

Example: A factory uses 100,000 MWh of electricity per year from the grid at an emission factor of 0.5 tCO2/MWh. They're considering three options:

 

• Option A: Switch to renewable energy. Costs $2M upfront, saves $500K/year on electricity

 

• Option B: Improve efficiency 20%. Costs $3M upfront, reduces electricity use to 80,000 MWh

 

• Option C: On-site solar for 30% of use. Costs $5M upfront, generates 30,000 MWh/year

 

Calculate emissions reduced and cost per ton for each option.

 

• Current emissions: 100,000 MWh × 0.5 tCO2/MWh = 50,000 tCO2/year

 

• Option A: Reduces all emissions = 50,000 tCO2/year saved. Net cost over 10 years = $2M - ($500K × 10) = -$3M (saves money). Cost per ton = -$3M / (50,000 × 10) = -$6/ton

 

• Option B: Reduces 20,000 MWh = 10,000 tCO2/year saved. Cost = $3M. Cost per ton = $3M / (10,000 × 10) = $30/ton

 

• Option C: Reduces 30,000 MWh = 15,000 tCO2/year saved. Cost = $5M. Cost per ton = $5M / (15,000 × 10) = $33/ton

 

Option A is clearly best if you can secure renewable energy contracts.

 

2. LCOE Calculations

 

Levelized cost of energy measures the total cost per unit of energy over a project's lifetime.

The formula is: LCOE = (Total lifetime costs) / (Total lifetime energy production)

 

Example: A solar project costs $10M upfront and $200K/year to operate. It produces 5,000 MWh/year for 25 years.

 

• Total costs = $10M + ($200K × 25) = $15M

 

• Total production = 5,000 MWh × 25 = 125,000 MWh

 

• LCOE = $15M / 125,000 MWh = $120/MWh

 

Compare this to current electricity costs to determine if it makes sense.

 

3. Payback Period

 

Payback period measures how long until an investment pays for itself?

 

Example: Switching to LED lighting costs $500K upfront and saves $100K/year in electricity costs.

 

Payback period = $500K / $100K = 5 years

 

In sustainability cases, also calculate the "carbon payback" - how long until emissions savings offset any emissions from manufacturing or installation.

 

4. Material Flow Analysis

 

For circular economy cases, you’ll need to use math to track materials through the system.

 

Example: A company produces 10,000 tons of product per year. Currently, 20% is made from recycled content. They want to reach 50% recycled content.

 

• Current recycled input = 10,000 × 20% = 2,000 tons

 

• Target recycled input = 10,000 × 50% = 5,000 tons

 

• Additional recycled material needed = 5,000 - 2,000 = 3,000 tons

 

Then calculate collection rates, sorting efficiency, and reprocessing costs to determine feasibility.

 

Answering Qualitative Questions in Your Sustainability Case Interview

 

Not everything in sustainability cases involves numbers. You'll need strong business judgment for questions like these.

 

Here are some examples of qualitative questions that could be asked in your sustainability case interview.

 

Example #1: Prioritizing Interventions

 

Question: We've identified 15 potential emissions reduction projects. How should we prioritize them?

 

You may want to consider:

 

• Cost effectiveness ($/ton CO2)

 

• Speed of implementation

 

• Co-benefits (cost savings, reduced risk, improved operations)

 

• Technical risk and dependencies

 

• Stakeholder visibility and impact

 

• Regulatory requirements

 

• Organizational capacity

 

Group projects into quick wins (low cost, high impact), strategic bets (high cost, high impact), and fill-ins (low cost, low impact). Skip high cost, low impact projects.

 

Example #2: Stakeholder Management

 

Question:  Our renewable energy transition will eliminate 200 jobs in our coal operations. How do we handle this?

 

Address both practical and ethical dimensions:

 

• Just transition principles and timing

 

• Retraining and redeployment options

 

• Severance packages and support

 

• Community economic development

 

• Transparent communication

 

• Union engagement

 

• Geographic diversification of impact

 

Example #3: Technology Selection

 

Question: Should we invest in proven technology with higher costs, or newer technology with lower costs but higher risk?

 

You may want to evaluate:

 

• Risk tolerance and financial position

 

• Timeline urgency

 

• Scale of deployment

 

• Vendor ecosystem and support

 

• Upgrade path and future-proofing

 

• Regulatory certainty

 

• Learning curve and experience

 

Often the right answer is a portfolio approach - deploy proven tech at scale while piloting new technology.

 

Example #4: Make vs. Buy Decisions

 

Question: Should we generate our own renewable energy or purchase it through contracts?

 

You may want to consider:

 

• Capital availability and cost of capital

 

• Core competencies

 

• Scale of energy needs

 

• Real estate and land availability

 

• Electricity market structure

 

• Flexibility and future options

 

• Balance sheet impacts

 

Purchasing through power purchase agreements often makes more sense for most companies.

 

Delivering a Recommendation in Your Sustainability Case Interview

 

The last step of a sustainability case interview is to deliver your ultimate recommendation to the client.

 

Unlike traditional cases, you’ll need to structure your final recommendation with both financial and sustainability metrics.

 

Start with your recommendation clearly.

 

Example: "The company should invest $50M in energy efficiency and renewable energy to reduce emissions 45% by 2030 while generating $10M in annual savings."

 

Next, support it with 2-3 key reasons:

 

Example:

 

• "This approach delivers a 3-year payback and 20% IRR, generating $200M in savings over 20 years."

 

• "It reduces 500,000 tons of CO2 annually, putting us on track for science-based targets and net zero by 2050."

 

• "It reduces exposure to carbon pricing, improves ESG ratings, and strengthens our position with environmentally-conscious customers."

 

Lastly, include next steps.

 

Example: "Immediate priorities are completing detailed engineering studies, securing board approval, and negotiating renewable energy contracts."

 

How to Prepare for Sustainability Case Interviews

 

Start with the fundamentals. If you haven't already, master traditional case interviews first. 

 

Afterwards, build sustainability-specific knowledge:

 

• Learn the basics. Spend a few hours understanding carbon accounting, renewable energy economics, and circular economy principles. You don't need deep expertise, just solid fundamentals

 

• Read industry reports. McKinsey, BCG, and Bain all publish sustainability reports. Read 3-4 recent ones to understand current issues and approaches

 

• Follow sustainability news. Read coverage in industry publications for 15-30 minutes daily to build intuition about what matters

 

Lastly, practice sustainability cases. Do 5-10 practice cases with sustainability topics. Many are available for free online on consulting firm websites or in MBA consulting casebooks.

 

Next Steps

 

You now understand what makes sustainability cases different from traditional cases and what knowledge you need to succeed.

 

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